This application claims the benefit of Korean Patent Application No. P2000-17026, filed on Mar. 31, 2000, which is hereby incorporated by reference for all purposes as if fully set forth herein.
1. Field of the Invention
This invention relates to an apparatus for mounting an integrated circuit on a liquid crystal display, and more particularly to a tape carrier package with a dummy bending part that is capable of reducing a difference in brightness in a screen. Also, the present invention is directed to a liquid crystal display that is capable of reducing a difference in brightness, using said tape carrier package.
2. Description of the Related Art
Generally, a liquid crystal display with an active matrix driving system uses thin film transistors (TFTs) as switching devices to display a natural moving picture. Since such a liquid crystal display can be made into a smaller-size device than the Brown tube, it is commercially available for a monitor such as a portable television or a lap-top personal computer, etc.
The active matrix liquid crystal display displays a picture corresponding to video signals, such as television signals, on a pixel (or picture element) matrix having pixels arranged at each intersection between gate lines and data lines. Each pixel includes a liquid crystal cell for controlling a transmitted light quantity in accordance with a voltage level of a data signal from a data line. The TFT is installed at an intersection between the gate line and the data line to switch a data signal to be transferred to the liquid crystal cell in response to a scanning signal (i.e., a gate pulse) from the gate line.
Such a liquid crystal display requires a number of driving integrated circuits, each hereinafter referred to as a xe2x80x9cD-ICxe2x80x9d, connected to the data lines and the gate lines to apply data signals and scanning signals to the data lines and the gate lines, respectively. The D-ICs are installed between the printed circuit board (PCB) and the liquid crystal panel to apply the data signals and the scanning signals to the data lines and the gate lines of the liquid crystal panel in response to a control signal applied from the PCB. A tape automated bonding (TAB) system has generally been used as a mounting method of the D-ICs that is capable of widening an effective area of the panel and has a relatively simple mounting process.
The TAB method may be divided into a bending type as shown in FIG. 1A, and a flat type as shown in FIG. 1B. The bending-type TAB system as shown in FIG. 1A has been used for a mounting of source and gate drivers of a monitor or a notebook computer. In the bending-type TAB system, a PCB 6 is folded to the rear side of a liquid crystal panel 2 by bending a tape carrier package (TCP) 10 mounted with a D-IC 8 and connected between a lower glass substrate 3 of the liquid crystal panel 2 and the PCB 6. A backlight unit 4 is positioned below the liquid crystal display panel 2. As shown in FIG. 2 and FIG. 3, an adhesive 25 is coated on a base film 24 of the TCP 10, and a lead part 26 is adhered thereon. The lead part 26 made from copper (Cu) is connected to pins of the D-IC 8. On the lead 26 is coated a solder resistor 27 responsible for providing an insulator. At the upper end and the lower end of the base film 24, an input pad part 21 and an output pad part 22 extending from each lead of the lead part 26 are provided. The input pad part 21 is connected to an output signal wiring of the PCB while the output pad part 22 is connected to the gate line or the data line formed on a lower glass substrate 3. Bending parts 10a and 10b are provided between the input pad part 21 and the D-IC 8 and between the output pad part 22 and the D-IC 8, respectively. The base film 24 is removed from the bending parts 10a and 10b. The TCP 10 is easily bent with the aid of these bending parts 10a and 10b. 
The flat-type TAB system as shown in FIG. 1B is mainly used to mount gate drivers of a 10.4xe2x80x3 or 12.1xe2x80x3 small-size notebook computer or monitor. In the flat-type TAB system, a TCP 12 mounted with a D-IC 8 and connected between a lower glass substrate 3 of a liquid crystal panel 2 and a PCB 6 is arranged in parallel to the liquid crystal panel 2. Thus, since the TCP 12 connected between the liquid crystal panel 2 and the PCB 6 is not bent, no bending part is formed.
However, the conventional TAB system has a problem in that a brightness difference is generated between an area where the TCP 10 or 12 is adhered onto the liquid crystal panel 2 and an area where the TCP 10 or 12 is not adhered onto the liquid crystal panel 2. More specifically, as shown in FIG. 4, the TCPs 10c to 10j are adhered to the edge of the lower glass substrate 3 at a desired spacing, having an anisotropic conductive film (ACF) therebetween under a high temperature and high pressure atmosphere. At this time, the TCPs 10c to 10j are expanded by heat and then contracted while the heat applied thereto is lowered to a normal temperature after their adhesion. A stress is applied to the lower glass substrate 3 by such TCPs 10c to 10j. As a result, since the lower glass substrate 3 is deformed into a periodical land/groove shape as shown in FIG. 5, a cell gap between an upper glass substrate (not shown) and the lower glass substrate 3 has a periodical thickness difference. When an experiment using the gray patterns of xe2x80x987xe2x80x99 and xe2x80x983xe2x80x99 was made with respect to two samples of a 12.1xe2x80x3 liquid crystal panel as shown in FIG. 4 having SVGA resolution (i.e., 800xc3x97600) and a brightness of 300 nit, a brightness difference is periodically generated. As a result of this experiment, a brightness difference between the adhesive areas a, c, e, g, i and k and the non-adhesive areas b, d, f, h and i of the TCPs 10c to 10j having a difference in the cell gap is indicated in the following Table 1, and in FIGS. 6 and 7. As a brightness measuring device, a xe2x80x98PR800xe2x80x99 model optical measuring-set is used for sensing a brightness level in accordance with a received light amount.
As seen from Table 1, a brightness difference is generated between the adhesive areas a, c, e, g, i and k and the non-adhesive areas b, d, f, h and l of the TCPs 10c to 10j. In two samples, average brightness differences in the 7 gray pattern and the 3 gray pattern have 0.2691 and 0.1957, respectively. Since a stress applied to the lower glass substrate 3 by the TCPs 10a to 10h becomes larger as the TCPs 10c to 10j become longer or thicker, a brightness difference between the adhesive areas a, c, e, g, i and k and the non-adhesive areas b, d, f, h and l of the TCPs 10c to 10j becomes larger. Therefore, a strategy capable of reducing a brightness difference caused by the TCPs 10c to 10j is required to improve a display quality of the liquid crystal display.
FIG. 6 is a characteristic diagram of a brightness level detected from the liquid crystal panel shown in FIG. 4 with respect to a 7-gray pattern;
FIG. 7 is a characteristic diagram of a brightness level detected from the liquid crystal panel shown in FIG. 4 with respect to a 3-gray pattern;
Accordingly, it is an object of the present invention to provide a tape carrier package with a dummy bending part that is capable of reducing a brightness difference of the screen.
A further object of the present invention is to provide a liquid crystal display that is adaptive for reducing a brightness difference of the screen.
In order to achieve these and other objects of the invention, a tape carrier package according to one aspect of the present invention includes a pad part connected to a liquid crystal panel; a base film mounted with an integrated circuit chip for applying a signal to the liquid crystal panel; and a dummy bending part for distributing a stress applied to the liquid crystal panel according to a thermal expansion of the pad part by removing the base film between the pad part and the integrated circuit chip.
A tape carrier package according another aspect of the present invention includes a base film mounted with an integrated circuit chip for applying a signal to a liquid crystal panel; a pad part extending from the integrated circuit chip to be connected to the liquid crystal panel; at least one bending part in which the base film at a portion where the tape carrier package is folded is removed; and at least one dummy bending part, in which a desired base film at a portion where the tape carrier package is not folded is removed, for reducing a thermal expansion force and a thermal contraction force of the base film parallel to the longitudinal direction of the integrated circuit chip.
A liquid crystal display device according to still another aspect of the present invention includes a liquid crystal panel; a tape carrier package connected to the liquid crystal panel; a base film mounted with an integrated circuit chip for applying a signal to the liquid crystal panel; at least one bending part in which the base film at a portion where the tape carrier package is folded is removed; a dummy bending part, in which the base film is removed in a direction perpendicular to terminals of the pad part, for reducing a thermal expansion force and a thermal contraction force generated at the time of thermal-pressing the pad onto the liquid crystal panel; and a printed circuit board connected to an input pad part of the tape carrier package.